ICF (Insulated Concrete Formwork) systems have been gaining popularity in New Zealand due to their ease of use and their versatility. They require minimal on-site equipment and because they are so light, building crews stay fresh throughout the day. They also place few limitations on the creative freedom of architects. 

Several ICF systems are available. All use stacked hollow polystyrene blocks to form the walls of the house, within which reinforcing steel is positioned and concrete poured to form the structural core of the wall.

Plastic or metal spacers run along the width of the block to tie together the inside and outside pieces of polystyrene. The composition of the blocks varies between manufacturers.  
 
In some systems, the spacers are part of the polystyrene form, while in other systems, the blocks are assembled and the spacers inserted on site.

Each block system has unique requirements, such as for reinforcing, wall thickness, etc, so it is important to find these out from the manufacturer/distributor before starting.

There are many advantages to this type of construction, for instance ICF:

• is easy to create curves and arches
• have a high thermal insulation value
• have a high acoustic insulation value
• allows for deep reveals at openings
• is a solid reinforced concrete construction
• multi-storey construction is easy, incorporating concrete floorswater evaporation is slowed down, which enhances the concrete's curing process and can result in stronger concrete
  

Some systems allow for the internal lining of polystyrene to be stripped away to reveal the inner concrete core. This enables the advantages of thermal mass to be available inside the home.

After construction of the ICF wall is complete and the structure is closed in, an acrylic plaster can be applied or traditional wall claddings can be fixed to the internal and external faces and finished in the normal manner.